Hubert Wiktor Askanas

Physiological stress of breeding Bicknell’s and Swainson’s Thrush.

M.Sc. defended September 2012

Science/Biology, University of New Brunswick, Fredericton

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phone: 459-3713


Research Description

Bicknell’s Thrush is one of two migratory birds in North America that exhibit a polygynandrous mating system. Hubert Askanas with a geolocator, retrieved from a Bicknell's Thrush (photo by Hubert Askanas)Having multiple male feeders at the nest, and a skewed sex ratio, suggests that Bicknell’s Thrush adults partition the feeding effort. Since nestling provisioning is physiologically stressful, we predicted that Bicknell’s Thrush would be less stressed than a monogamous counterpart during the nestling provisioning period of the breeding season. We compared Bicknell’s Thrush with Swainson’s Thrush, a close relative and concurrent monogamous breeder in our study area. Feeding rates were obtained by recording video of nests. We speculated the presence of a cohort of male Bicknell’s Thrush that provided less often. As our study used heterophil to lymphocyte ratio (H:L), as a surrogate for corticosterone in the analysis of physiological stress, we tested for any effects of parasitism on relative leukocyte profile. We also tested the sensitivity of H:L to physiological stress, by comparing breeding and overwintering birds. Last of all, we tested whether H:L could be a suitable tool for deducing nest success, for demographic studies where catching adults is easier than finding nests.

Photo by Hubert Askanas of a Bicknell's Thrush.

Special Interests:

Let’s Talk Science, science outreach program


  • Askanas, H. W. 2011. The Physiological Stress of Two Closely-related Songbirds During Their Breeding Season: the Polygynandrous Bicknell’s Thrush (Catharus bicknelli) and the Socially Monogamous Swainson’s Thrush (Catharus ustulatus). Picoides 24 (1):15.


  • Askanas, H. W., Fraser, K. C., Diamond, A. W. 2007. The effects of polygynandrous mating on the immune system of Catharus bicknelli. Poster presentation at the International Bicknell’s Thrush Conservation Group (IBTCG) inaugural meeting Woodstock, VT ; and Atlantic Cooperative Wildlife Ecology Research Network conference, Sackville, New Brunswick.
  • Askanas, H. W., Diamond, A. W., Fraser, K. C., Holberton, R. , Leppert, L. 2009. The effects of mating systems on the physiological stress of two closely- related song birds; the polygynandrous Bicknell’s Thrush (Catharus bicknelli) and socially monogamous Swainson’s Thrush (Catharus ustulatus). Poster presentation at the joint Wilson Ornithological Society and Association of Field Ornithologists conference, Pittsburgh, Pennsylvania.



  • Askanas, H. W., Diamond, A.W., Fraser, K.C., Holberton, R. , Leppert, L. 2011. The breeding behaviour and physiological stress of Bicknell’s and Swainson’s Thrush in the Christmas Mountains, New Brunswick. Oral presentation at the Society of Canadian Ornithologists/Société des Ornithologistes du Canada conference, Sackville, New Brunswick.